This research is directed towards elucidation of the function of phosphorylated proteins and the associated protein phosphorylation and dephosphorylation reactions in the cell nucleus. The current phase of the work is concentrated on the study of histone phosphorylation and histone phosphorylating enzymes which occur specifically in growing cells, and on the function of hormone-regulated histone phosphorylation in structural changes in chromatin which may facilitate RNA synthesis. Using methodology developed in the course of identifying specific phosphorylation sites in lysine-rich Hl histone, the study of the phosphorylation of individual sites in the histone under various conditions of growth and hormone-stimulation will be extended, in hopes of determining the role of the various types of histone phosphorylation in these processes. Examination of cells for the presence of enzymes catalyzing the specific phosphorylation of other histones will also be carried out, and collaborative studies on the effects of phosphorylation on the interaction of histones with DNA and other chromosomal components will be continued. BIBLIOGRAPHIC REFERENCES: Inglis, R.J., Langan, T.A., Matthews, H.R., Hardie, D.G. and Bradbury, E.M.: Advance of Mitosis by Histone Phosphokinase. Exper. Cell Res., 97, 418-425 (1976). Langan, T.A.: Characterization of growth-associated phosphorylation sites in calf thymus lysine-rich (H1) histone. Fed. Proc. 35, 1623 (1976).